Cod sursa(job #284964)

Utilizator taloibogdanTaloi Bogdan Cristian taloibogdan Data 22 martie 2009 09:55:49
Problema Fractii Scor 100
Compilator cpp Status done
Runda petru_toti Marime 0.35 kb
Raporteaza aceasta sursa 
#include<stdio.h>
long n,i,f[1000050],j;
long long nr;
int main()
{
 freopen("fractii.in","r",stdin);
 freopen("fractii.out","w",stdout);
 scanf("%ld",&n);
 for(i=2;i<=n;++i)f[i]=i;
 for(i=2;i<=n;++i)
    if(f[i]==i){for(j=1;i*j<=n;++j)f[i*j]=(f[i*j]/i)*(i-1);}
 nr=1ll;
 for(i=2;i<=n;++i)nr+=(2*f[i]);
 printf("%lld\n",nr);
 return 0;
}